Random black line appearing on glass texture from interaction of noise & fresnel node
How about something like this :



The Bump node uses the Noise to generate a Normal for the shaders. The 'bumpiness' can be adjusted via the Distance of the bump node. The Layer Weight node can be adjusted to vary the amount the angle with the glass affects the bumpiness (so shallower angles appear more bumpy while 'straight on' viewing is effectively flat).

Note that this is obviously a non-physically based material (since the bumpiness is directly affected by the viewing angle).